So now I installed my new Artic Freezer 64. The installation, apart from removing the old heatsink, was an easy task. But when I booted my PC for the first time, the cpu temp readings in my BIOS showed 54°. The cpu temp reading in windows (speedfan) showed 24°.
I know the readings in the BIOS are more accurate, but it's hard to believe these are correct. I am almost sure the new heatsink has been installed correctly. Should I trust the readings from speedfan ?

Anyway, I'll do a decent testrun tomorrow and touch the copper piece of the heatsink with my hand.